The field of invention is seats and chairs with heat exchange and the invention is particularly concerned with a heating conductor connection between electrically heated seat and backrest surfaces. The seat and backrest are separated by a bracing trough provided in the padding, core and beneath the bracing trough a bracing wire is provided which is bonded into the padding core. The bracing wire is exposed in sections by window-like recesses in the bracing trough, and, furthermore, the connecting seam of the covering materials (textile, leather or plastic) are likewise provided in the bracing trough. The covering materials include an apron which is formed by an insert loop and which receives a further bracing wire, for heating the seats of vehicles.
The prior art electrical connections between two or more heated surfaces of a vehicle seat are particularly liable to break under tensile, compressive and bending stresses.
In addition, between the heated surfaces, as mentioned a bracing trough or pit, i.e. a depression, is disposed in which a bracing apron connected to the covering material is arranged, this apron serving to secure and tension the cover over a bracing wire introduced into the apron.
This upper bracing wire is connected by clips through cutouts in the seat core to a second bracing wire embedded in the seat core.
There is a danger in this prior art solution that in the region of the heating conductor connection between the otherwise separate heating faces local overheating of the heating conductors occurs. This overheating leads to damage and destruction of the insulation and scaling of the fine heating conductor stranded wire which then in conjunction with the afore-mentioned possible mechanical stresses finally leads to breakage of the individual wires.
The resulting reduction of the heating conductor crosssection leads to a further increase in the local overheating so that the heating conductor finally burns through completely and usually leaves a visible scorched area.
Various attempts have been made to eliminate this source of danger. Thus, for example, in some cases a lateral bypassing of the bracing point is used. This is, however, usually not possible because such a procedure does not permit the formation of exact edge borders of the heating surfaces.
A prior art construction similar to this lateral bypass construction is described by German Utility Model No. 81 37 914.5. This connecting means between several surface heating element sections aims at avoiding the danger due to mechanical stresses by forming a connection which includes between the connection points of the individual surface heating sections multicore conductor stranded wires laid in waves. The conductor stranded wires are connected to the terminal wires on both sides by crimped sleeves so that the terminal wires, each surrounded by the conductor cores, are pressed into the crimped sleeve.
The use of a conductor stranded wire which is thick and flexible enough to stand up to the mechanical requirements avoids, due to its large cross-section, the danger of local overheating.
Fundamentally, however, this connection has the disadvantage that the heating conductor must be interrupted and in each case two connection points arise for heating the wire-conductor stranded wire. When these connections lie in the heating surface they form hard points which can be seen in the covering material disposed thereabove, and can be felt therethrough. This is particularly true with leather and velour.
When these prior art connections are accommodated in the bracing troughs they are subjected to an increased mechanical stress which can easily lead to tearing of heating conductors because of their stiffness.
It has been found in practice that the connection of a thin wire cross-section to the cross-section of a stranded wire several times thicker is always problematical.
In addition, the laying within the bracing trough always requires great care which cannot usually be assumed in the assembly of vehicle seats carried out at piece rate.